Defining Receptors and Hypotheses

b. Research should not be incorporated into the assessments (because

research efforts are uncertain by nature, and the cost should not be borne

by a specific project).

c. An intuitive, common sense approach should be used to distinguish when

to use a "back of the envelope" approach and when to use a "full" risk

assessment.

d. Physical and chemical stressors should be addressed.

e. Stakeholders should be engaged as part of the initial assessment.

Defining Receptors and Hypotheses

The workgroup was mindful that the exposure assessment and the development

of conceptual models could easily become a dilute repository for remote issues

which do not pass the test of "reasonable concern." They felt that hypothesis

testing and a clear definition of who or what we are trying to protect should drive

the development of the exposure assessment. In particular, the identification of the

protected entity was an ever-present concern guiding the workgroup discussions.

The group noted that hypothesis testing and clearly defining the protected entity

are important in constraining the exposure analysis, adding rationality to risk

assessment, and in setting spatial and temporal limits for exposure models.

Likely Exposure Pathways

in Dredged Material Management

The workgroup developed a matrix (Table 1) which summarizes our opinions

regarding the likely exposure pathways for five commonly considered dredged

material management options: Unconfined Aquatic Disposal, Subaqueous

Confined Aquatic Disposal (CAD), Upland Disposal in a regulated landfill,

Upland Confined Disposal Facilities (CDF), and the No-Action Alternative. This

matrix indicates whether the pathway is a short- or long-term (S or L) concern for

a particular alternative. Note that the matrix includes diffusion as a potential

pathway, but the workgroup considered this pathway to be of minor or no concern

based on information in the scientific literature.

There was particular concern with the fish ingestion pathway for humans and

the development of ingestion rates. The general consensus was for using region-

specific rates which incorporate the fraction of diet affected by a site. Exposure

Chapter 2 Exposure Assessment Workgroup Summary